U.S. patent application number 13/349450 was filed with the patent office on 2012-07-19 for electric storage device.
This patent application is currently assigned to GS Yuasa International Ltd.. Invention is credited to Hajime KAWAMOTO, Jun Nakamura, Masakazu Tsutsumi.
Application Number | 20120183845 13/349450 |
Document ID | / |
Family ID | 45445967 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120183845 |
Kind Code |
A1 |
KAWAMOTO; Hajime ; et
al. |
July 19, 2012 |
ELECTRIC STORAGE DEVICE
Abstract
An electric storage device includes: an electrode assembly; a
case that houses the electrode assembly, the case including a
defining wall; a rivet that passes through the defining wall, the
rivet having a body and an insertion part formed continuously with
the body; a conductive member that is electrically connected to the
rivet; and a sealing member arranged at least one of between the
defining wall and the conductive member and between the defining
wall and the body. The insertion part has a portion that is
inserted through the defining wall, the sealing member and the
conductive member. The insertion part has a diameter smaller than
that of the body at least in the portion inserted through the
defining wall, the sealing member and the conductive member. The
insertion part has a hollow shaft-shaped end with a non-through
hole extending in an axial direction of the insertion part.
Inventors: |
KAWAMOTO; Hajime; (Osaka,
JP) ; Tsutsumi; Masakazu; (Kyoto-shi, JP) ;
Nakamura; Jun; (Kyoto-shi, JP) |
Assignee: |
GS Yuasa International Ltd.
Kyoto-shi
JP
|
Family ID: |
45445967 |
Appl. No.: |
13/349450 |
Filed: |
January 12, 2012 |
Current U.S.
Class: |
429/179 ;
361/502 |
Current CPC
Class: |
H01M 50/15 20210101;
Y02E 60/10 20130101; H01M 10/0413 20130101; H01M 50/172 20210101;
H01M 50/155 20210101; H01M 50/543 20210101; H01M 50/103 20210101;
H01M 50/531 20210101; H01M 50/183 20210101 |
Class at
Publication: |
429/179 ;
361/502 |
International
Class: |
H01M 2/30 20060101
H01M002/30; H01G 9/155 20060101 H01G009/155; H01M 2/08 20060101
H01M002/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2011 |
JP |
2011-007148 |
Claims
1. An electric storage device comprising: an electrode assembly; a
case that houses the electrode assembly, the case including a
defining wall; a rivet that passes through the defining wall, the
rivet having a body and an insertion part formed continuously with
the body; a conductive member that is electrically connected to the
rivet; and a sealing member arranged at least one of between the
defining wall and the conductive member and between the defining
wall and the body, wherein the insertion part has a portion that is
inserted through the defining wall, the sealing member and the
conductive member; the insertion part has a diameter smaller than
that of the body at least in the portion inserted through the
defining wall, the sealing member and the conductive member; the
insertion part has a hollow shaft-shaped end with a non-through
hole extending in an axial direction of the insertion part, the end
being crimped in a state where the insertion part has been inserted
through the defining wall, the sealing member and the conductive
member; and a bottom of the non-through hole is located between the
defining wall and the conductive member.
2. The electric storage device according to claim 1, wherein the
insertion part is inserted through the defining wall toward the
conductive member; and the sealing member comprises two sealing
members, one of which is arranged between the defining wall and the
conductive member and the other of which is arranged between the
defining wall and the body.
3. The electric storage device according to claim 2, herein at
least one of the sealing members has an annular projection that is
inserted through the defining wall; and the annular projection is
inserted through the defining wall while covering the periphery of
the insertion part.
4. The electric storage device according to claim 1, wherein the
end of the insertion part is crimped to have a thickness, which
decreases as the end of the insertion part advances away from the
axis of the insertion part.
5. The electric storage device according to claim 1, wherein the
insertion part is crimped only at the hollow shaft-shaped portion
of the non-through hole.
6. The electric storage device according to claim 1, wherein the
bottom of the non-through hole is located at a position between the
defining wall and the conductive member and close to the conductive
member.
7. The electric storage device according to claim 6, wherein the
bottom of the non-through hole has a tapered shape.
8. The electric storage device according to claim 1, wherein the
body has a shaft shape extending along the axis of the insertion
part.
9. The electric storage device according to claim 1, wherein the
conductive member is a current collector arranged inside the case,
the current collector being electrically connected to the electrode
assembly; the sealing member comprises an inner sealing member
arranged on an inner surface of the defining wall; and the
insertion part is inserted through the defining wall, the inner
sealing member and the current collector from outside the case to
inside the case.
10. The electric storage device according to claim 1, wherein the
conductive member is a current collector arranged inside the case,
the current collector being electrically connected to the electrode
assembly; the sealing member comprises an outer sealing member
arranged on an outer surface of the defining wall; and the
insertion part is inserted through the outer sealing member, the
defining wall and the current collector from outside the case to
inside the case.
11. The electric storage device according to claim 1, wherein the
conductive member is a drawing member arranged outside the case;
the sealing member comprises an inner sealing member arranged on an
inner surface of the defining wall; and the insertion part is
inserted through the inner sealing member, the defining wall and
the drawing member from inside the case to outside the case.
12. The electric storage device according to claim 1, wherein the
conductive member is a drawing member arranged outside the case;
the sealing member comprises an outer sealing member arranged on an
outer surface of the defining wall; and the insertion part is
inserted through the defining wall, the outer sealing member and
the drawing member from inside the case to outside the case.
13. The electric storage device according to claim 1, wherein the
conductive member is a current collector arranged inside the case,
the current collector being electrically connected to the electrode
assembly; the sealing member comprises an inner sealing member
arranged on an inner surface of the defining wall and an outer
sealing member arranged on an outer surface of the defining wall;
and the insertion part is inserted through the outer sealing
member, the defining wall, the inner sealing member and the current
collector from outside the case to inside the case.
14. The electric storage device according to claim 1, wherein the
conductive member is a drawing member arranged outside the case;
the sealing member comprises an outer sealing member arranged on an
outer surface of the defining wall and an inner sealing member
arranged on an inner surface of the defining wall; and the
insertion part is inserted through the inner sealing member, the
defining wall, the outer sealing member and the drawing member from
inside the case to outside the case.
15. The electric storage device according to claim 1, wherein the
case includes a case body having an opening and a cover plate that
covers and seals the opening of the case body; and the rivet passes
through the cover plate that is a portion of the defining wall of
the case.
16. The electric storage device according to claim 15, wherein the
case body has a rectangular box shape that is flat in the width
direction; and the cover plate is a rectangular plate that
corresponds in position to the opening of the case body.
17. The electric storage device according to claim 16, wherein the
rivet includes a pair of rivets, the pair of rivets passing through
the cover plate at two locations that are spaced from each other in
the longitudinal direction of the cover plate.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Japanese Patent
Application No. 2011-007148, the disclosure of which is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to an electric storage device
including an electrode assembly, a case that houses the electrode
assembly, and a rivet that passes through a defining wall of the
case.
BACKGROUND ART
[0003] In recent years, rechargeable and dischargeable electric
storage devices such as battery cells (e.g., a lithium ion battery
cell and a nickel-metal hydride battery cell) and capacitors (e.g.,
an electric double layer capacitor) have been adopted as the power
sources of vehicles (e.g., an automobile and a motorcycle) and
various devices (e.g., a portable terminal and a laptop computer).
For example, various types of battery cells have been provided. One
of them is a battery cell that includes: an electrode assembly; a
current collector that is electrically connected to the electrode
assembly; a case that houses the electrode assembly and the current
collector; an external terminal arranged outside the case; an inner
sealing member arranged along the inner surface of a defining wall
of the case; an outer sealing member arranged along the outer
surface of the defining wall; and a rivet that is inserted through
the defining wall, the inner sealing member and the outer sealing
member, wherein the external terminal and the current collector are
electrically connected to each other via the rivet.
[0004] The rivet includes an electrically conductive material. The
rivet includes: a shaft-shaped body; and a solid shaft-shaped or
hollow shaft-shaped (tubular) insertion part which is formed
continuously with the body. The outer diameter of the insertion
part is sized to be smaller than the outer diameter of the body.
The insertion part is inserted through the defining wall of the
case, the inner sealing member, the outer sealing member and the
current collector, and in this state, the insertion part is crimped
at an end (cf., JP-A-2002-324541 (Patent Document 1), for
example).
[0005] As a result, the end of the insertion part of the rivet has
an enlarged diameter. That is, in a battery cell using a rivet
having a solid shaft-shaped insertion part, the end of the
insertion part of the rivet is completely flattened with the
diameter enlarged. In a battery cell using a rivet having a hollow
shaft-shaped insertion part, the end of the insertion part of the
rivet is flattened while being forced radially outward to be
deformed into a flange shape.
[0006] Accordingly, in these battery cells, the rivet integrally
unites the defining wall of the case, the inner sealing member, the
outer sealing member and the current collector between the body and
the crimped end, which apply a compressive force to the peripheral
area of the through-hole through which the rivet has been inserted.
As a result, the inner and outer sealing members are brought into
close contact with the defining wall of the case to seal the
through-hole through which the rivet has been inserted, thereby
providing sealing within the case. Also, the current collector and
the electrode assembly are fixed to the case via the rivet.
[0007] According to a rivet having a solid shaft-shaped insertion
part, it may not be possible to crimp the end of the insertion part
of the rivet sufficiently by a single crimping operation because of
the high stiffness of the insertion part. This means several
crimping operations are required. However, repeated crimping
operations cause high force to act on the rivet each time the
crimping is performed, which could result in deformation of the
defining wall of the case.
[0008] If this occurs, the degree of contact of the inner and outer
sealing members with the defining wall decreases, leading to the
possibility that sealing of the case may be not be ensured. In
particular, when the case includes an aluminum alloy to reduce the
weight of the battery cell, deformation of the defining wall caused
by the crimping of the rivet becomes significant due to the
softness of an aluminum alloy compared to steel such as stainless
steel and the like, resulting in a sharp decrease of sealing of the
case.
[0009] In contrast, with a rivet having a hollow shaft-shaped
insertion part, the end of the insertion part is easily deformed by
crimping because the insertion part is thin walled with its central
portion being hollow.
[0010] However, the hollow shaft-shaped insertion part has a lower
stiffness than the solid shaft-shaped insertion part. Because of
this, at the time of crimping, the end of the insertion part may
not be completely expanded outward but partly forced toward the
hollow portion. If this occurs, the end of the insertion part may
not be formed into a flange shape having an outer diameter
sufficient to hold the periphery of the through-hole through which
the rivet has been inserted.
[0011] Accordingly, even with the rivet having a hollow
shaft-shaped insertion part, it is sometime impossible to ensure
sealing of the case as with the rivet having a solid shaft-shaped
insertion part.
[0012] This problem occurs not only in battery cells but also in
capacitors (e.g., a double layer capacitor and the like) as
well.
SUMMARY OF THE INVENTION
[0013] An object of the present invention is to provide an electric
storage device that can ensure sealing of a case.
[0014] An electric storage device according to the present
invention includes:
[0015] an electrode assembly;
[0016] a case that houses the electrode assembly, the case
including a defining wall;
[0017] a rivet that passes through the defining wall, the rivet
having a body and an insertion part formed continuously with the
body;
[0018] a conductive member that is electrically connected to the
rivet; and
[0019] a sealing member arranged at least one of between the
defining wall and the conductive member and between the defining
wall and the body,
[0020] wherein the insertion part has a portion that is inserted
through the defining wall, the sealing member and the conductive
member;
[0021] the insertion part has a diameter smaller than that of the
body at least in the portion inserted through the defining wall,
the sealing member and the conductive member;
[0022] the insertion part has a hollow shaft-shaped end with a
non-through hole extending in an axial direction of the insertion
part, the end being crimped in a state where the insertion part has
been inserted through the defining wall, the sealing member and the
conductive member; and
[0023] a bottom of the non-through hole is located between the
defining wall and the conductive member.
[0024] In an embodiment of the present invention, the electric
storage device may have a configuration in which:
[0025] the insertion part is inserted through the defining wall
toward the conductive member; and
[0026] the sealing member comprises two sealing members, one of
which is arranged between the defining wall and the conductive
member and the other of which is arranged between the defining wall
and the body.
[0027] In this instance,
[0028] at least one of the sealing members may have an annular
projection that is inserted through the defining wall; and
[0029] the annular projection may be inserted through the defining
wall while covering the periphery of the insertion part.
[0030] In another embodiment of the present invention, the electric
storage device may have a configuration in which:
[0031] the end of the insertion part is crimped to have a
thickness, which decreases as it advances away from the axis of the
insertion part.
[0032] In still another embodiment of the present invention, the
electric storage device may have a configuration in which:
[0033] the insertion part is crimped only at the hollow
shaft-shaped portion of the non-through hole.
[0034] In still another embodiment of the present invention, the
electric storage device may have a configuration in which:
[0035] the bottom of the non-through hole is located at a position
between the defining wall and the conductive member and close to
the conductive member.
[0036] In yet another embodiment of the present invention, the
electric storage device may have a configuration in which:
[0037] the bottom of the non-through hole has a tapered shape.
[0038] In another embodiment of the present invention, the electric
storage device may have a configuration in which:
[0039] the body has a shaft shape extending along the axis of the
insertion part.
[0040] In still another embodiment of the present invention, the
electric storage device may have a configuration in which:
[0041] the conductive member is a current collector arranged inside
the case, the current collector being electrically connected to the
electrode assembly;
[0042] the sealing member comprises an inner sealing member
arranged on an inner surface of the defining wall; and
[0043] the insertion part is inserted through the defining wall,
the inner sealing member and the current collector from outside the
case to inside the case.
[0044] In yet another embodiment of the present invention, the
electric storage device may have a configuration in which:
[0045] the conductive member is a current collector arranged inside
the case, the current collector being electrically connected to the
electrode assembly;
[0046] the sealing member comprises an outer sealing member
arranged on an outer surface of the defining wall; and
[0047] the insertion part is inserted through the outer sealing
member, the defining wall and the current collector from outside
the case to inside the case.
[0048] In another embodiment of the present invention, the electric
storage device may have a configuration in which:
[0049] the conductive member is a drawing member arranged outside
the case;
[0050] the sealing member comprises an inner sealing member
arranged on an inner surface of the defining wall; and
[0051] the insertion part is inserted through the inner sealing
member, the defining wall and the drawing member from inside the
case to outside the case.
[0052] In still another embodiment of the present invention, the
electric storage device may have a configuration in which;
[0053] the conductive member is a drawing member arranged outside
the case;
[0054] the sealing member comprises an outer sealing member
arranged on an outer surface of the defining wall; and
[0055] the insertion part is inserted through the defining wall,
the outer sealing member and the drawing member from inside the
case to outside the case.
[0056] In yet another embodiment of the present invention, the
electric storage device may have a configuration in which;
[0057] the conductive member is a current collector arranged inside
the case, the current collector being electrically connected to the
electrode assembly;
[0058] the sealing member comprises an inner sealing member
arranged on an inner surface of the defining wall and an outer
sealing member arranged on an face of the defining wall; and
[0059] the insertion part is inserted through the outer sealing
member, the defining wall, the inner sealing member and the current
collector from outside the case to inside the case.
[0060] In another embodiment of the present invention, the electric
storage device may have a configuration in which:
[0061] the conductive member is a drawing member arranged outside
the case;
[0062] the sealing member comprises an outer sealing member
arranged on an outer surface of the defining wall and an inner
sealing member arranged on an inner surface of the defining wall;
and
[0063] the insertion part is inserted through the inner sealing
member, the defining wall, the outer sealing member and the drawing
member from inside the case to outside the case.
[0064] In still another embodiment of the present invention, the
electric storage device may have a configuration in which:
[0065] the case includes a case body having an opening and a cover
plate that covers and hermetically seals the opening of the case
body; and
[0066] the rivet passes through the cover plate that is a portion
of the defining wall of the case.
[0067] In this instance,
[0068] the case body may have a rectangular box shape that is flat
in the width direction; and
[0069] the cover plate may be a rectangular plate that corresponds
in shape to the opening of the case body.
[0070] Furthermore, in this instance,
[0071] the rivet may include a pair of rivets, the pair of rivets
passing through the cover plate at two locations that are spaced
from each other in the longitudinal direction of the cover
plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] FIG. 1 is a perspective view of a battery cell according to
an embodiment of the present invention;
[0073] FIG. 2 is a side view of the battery cell;
[0074] FIG. 3 is a cross-sectional view taken along line A-A in
FIG. 1;
[0075] FIG. 4 is a cross-sectional view taken along line B-B in
FIG. 1;
[0076] FIG. 5 is an enlarged cross-sectional view of a terminal
part of the battery cell;
[0077] FIG. 6 is an enlarged cross-sectional view of a rivet and
its vicinity;
[0078] FIG. 7 is an exploded perspective view of the terminal part
as seen from above;
[0079] FIG. 8 is an exploded perspective view of the terminal part
as seen from below; and
[0080] FIG. 9 is an enlarged cross-sectional view of a terminal
part of a battery cell according to another embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0081] A battery cell which is an embodiment of an electric storage
device according to the present invention will be described below
with reference to the drawings. A battery cell according to the
present embodiment is a non-aqueous electrolyte secondary battery
cell and, more particularly, a lithium ion secondary battery cell.
As shown in FIGS. 1 to 4, the battery cell according to the present
embodiment includes a case 1 which is composed of a case body 2 and
a cover plate 3 which covers an opening of the case body 2 to seal
the case 1. The cover plate 3 includes terminal structures 9 which
are electrically connected to an electrode assembly 4 housed in the
case 1.
[0082] The case body 2 and the cover plate 3 include a metal such
as an aluminum alloy, a stainless alloy and the like. In this
embodiment, the case body 2 and the cover plate 3 include an
aluminum alloy. The adopted aluminum alloys include an untreated
aluminum alloy (F-temper material), an annealed aluminum alloy
(O-temper material), a work-hardened aluminum alloy (H-temper
material) and a heat treated aluminum alloy other than the above
(T-temper material). The case body 2 has a rectangular box shape
that is flat in the width direction, so that it houses a winding
type electrode assembly 4 that has been formed into an elliptic
cylinder. The cover plate 3 is a rectangular plate that corresponds
in shape to the opening of the case body 2.
[0083] As shown in FIGS. 5-8, the cover plate 3 has two
through-holes 3a, which are spaced from each other in the
longitudinal direction, each designed for insertion of a later
described rivet 12. The peripheral area of each through-hole 3a is
compression formed in the thickness direction by coining, for
example. This makes the peripheral area of each through-hole 3a
thinner than the remaining area. The compression forming of the
peripheral area of each through-hole 3a causes work hardening of
the peripheral area of each through-hole 3a, which results in an
increase in stiffness.
[0084] The peripheral areas of the through-holes 3a are made
thinner by compression forming, and the cover plate 3 is therefore
provided with recesses (first recesses) 3b in the outer surface,
into which outer gaskets 11 can be fitted.
[0085] Returning to FIGS. 1-4, the cover plate 3 is fitted into the
opening of the case body 2 and hermetically fixed by laser welding
or the like.
[0086] In the electrode assembly 4, a band-shaped positive
electrode sheet 5 and a band-shaped negative electrode sheet 6
which are displaced to each other in different lateral directions
with a band-shaped separator 7 sandwiched therebetween are wound
about a lateral rotation axis into a cylinder in the shape of a
vertically long ellipse. The electrode assembly 4 is entirely
covered with an insulating cover (not shown) including an
insulating sheet and is housed in the case 1 while being insulated
from the case 1. The positive electrode sheet 5 includes aluminum
foil carrying a positive electrode active material at the surface.
The negative electrode sheet 6 includes copper foil carrying a
negative electrode active material at the surface. The positive
electrode sheet 5 and the negative electrode sheet 6 each have a
non-overlapped portion not coated with the active material at an
edge in the lateral direction in which the sheet is displaced. With
this arrangement, at the lateral ends of the electrode assembly 4,
the aluminum foil and copper foil are exposed, and thus these metal
foils of the positive electrode and negative electrode project from
the overlapped portion in a wound configuration.
[0087] Metal foils projecting at the lateral ends of the electrode
assembly 4 are electrically connected to respective current
collectors 8. The current collectors 8 are vertically long
conductive metal members. More specifically, the current collector
8 for the positive electrode includes aluminum or an aluminum
alloy, and the current collector 8 for the negative electrode
includes copper or a copper alloy. An upper part of each current
collector 8 is horizontally bent to constitute a connection part
8a. A part extending downward from the connection part 8a is
divided into a front part and a rear part, which project downward.
The two front and rear parts are sandwiched between holding plates
(not shown) together with the corresponding end of the electrode
assembly 4 and are connected and fixed by ultrasonic welding or the
like.
[0088] The terminal structures 9 include a terminal structure 9 for
the positive electrode and a terminal structure 9 for the negative
electrode. As shown in more detail in FIGS. 5-8, each terminal
structure 9 includes a plastic plate 10, an outer gasket 11, a
rivet 12, a terminal retainer 13, a terminal bolt 14, and a drawing
member 15. The plastic plate 10 and outer gasket 11 are arranged
inside and outside the case 1 with through-holes 3a formed in the
right and left ends of the cover plate 3 interposed therebetween.
The rivet 12 is inserted into the through-hole 3a via the plastic
plate 10 and outer gasket 11 and is electrically connected to the
connection part 8a of the current collector 8. The terminal
retainer 13 is arranged close to the outer gasket 11. The terminal
bolt 14 is arranged at an outer surface of the cover plate 3 via
the terminal retainer 13. The drawing member 15 electrically
connects the terminal bolt 14 and the rivet 12. With this
configuration, the electrode assembly 4 inside the case 1 and the
terminal bolt 14 are electrically connected to each other.
[0089] It is to be noted that the plastic plate 10 and the outer
gasket 11 each correspond to a sealing member. Also, the plastic
plate 10, the outer gasket 11 and the terminal retainer 13 each
correspond to an insulating member. The rivet 12 corresponds to an
auxiliary terminal. The terminal bolt 14 represents an external
terminal. The drawing member 15 corresponds to a conductive
member.
[0090] The plastic plate 10 is a synthetic resin with insulating
and sealing properties. More specifically, for example,
polyphenylene sulfide (PPS) resin is used as the material for the
plastic plate 10. However, the material is not limited to this, and
any appropriate material can be selected. The plastic plate 10 has
a rectangular shape. A lower surface of the plastic plate 10
includes a recess 10a which can receive the connection part 8a of
the current collector 8. The plastic plate 10 includes a
through-hole 10b which coincides in position with a through-hole 8b
formed in the connection part 8a while the recess 10a receives the
connection part 8a of the current collector 8.
[0091] The outer gasket 11 is a synthetic resin with insulating
properties and sealing properties. More specifically, for example,
polyphenylene sulfide (PPS) resin is used as the material for the
plastic plate 10. However, the material is not limited to this, and
any appropriate material can be selected.
[0092] The outer gasket 11 is slightly larger than a body 12a of
the rivet 12 and has a rectangular shape. The outer gasket 11
includes a surrounding circumferential outer wall part 11a at the
outer periphery, which is formed by recessing an upper surface
except for the outer periphery. The outer gasket 11 includes a
recess 11b which can receive the body 12a of the rivet 12 inside
the outer wall part 11a. The outer gasket 11 includes a
through-hole 11c into which a first crimping part 12b of the rivet
12 can be inserted while the recess 11b receives the body 12a of
the rivet 12. A lower surface of the outer gasket 11 includes an
annular projection 11d which extends through the through-hole 3a of
the cover plate 3 and is inserted into the through-hole 10b of the
plastic plate 10.
[0093] Note that the plastic plate 10 is arranged on a lower
surface (an inner surface) of the cover plate 3 and is thus
arranged inside the case 1. The outer gasket 11 is arranged at an
upper surface (the outer surface) of the cover plate 3 and is thus
arranged at an outer surface of the case 1. A region of the upper
surface of the cover plate 3 where the outer gasket 11 is arranged
includes a non-circular recess (first recess) 3b which can receive
a lower part (bridge part) of the outer gasket 11. When the lower
part (a joining surface to the cover plate 3) of the outer gasket
11 is inserted into the first recess 3b, the outer gasket 11 is
restrained from rotating about its axis. Note that, in the present
embodiment, the first recess 3b is formed to be rectangular so as
to correspond to the shape of the rectangular lower part of the
outer gasket 11. The first recess 3b is formed by coining or the
like.
[0094] The rivets 12 include a rivet 12 on the positive electrode
side and a rivet 12 on the negative electrode side. The rivet 12 on
the positive electrode side is a conductive metal member including
aluminum or an aluminum alloy. The rivet 12 on the negative
electrode side is a conductive metal member including copper or a
copper alloy. As shown in FIGS. 7 and 8, the rivet 12 has a first
crimping part 12b as an insertion part projecting downward from the
lower surface of the body 12a. The rivet 12 has a second crimping
part 12c as another insertion part projecting upward from the upper
surface of the body 12a. The first crimping part 12b and the second
crimping part 12c each look like a shaft and have a smaller
diameter than the body 12a.
[0095] The body 12a has a shaft shape. The body 12a has an outer
diameter larger than the diameter of the through-hole 3a of the
cover plate 3. The body 12a has four flat surfaces (no reference
numbers are allocated), which are evenly spaced apart in the
circumferential direction, on the outer circumference. Each of the
four flat surfaces faces the inner wall surface of the outer wall
part 11a of the outer gasket 11 with the body 12a received in the
recess 11b of the outer gasket 11.
[0096] The first crimping part 12b is a portion that is inserted
through the through-hole 3a of the cover plate 3, the through-hole
8b of the connection part 8a of the current collector 8, the
through-hole 10b of the plastic plate 10 and the through-hole 11c
of the outer gasket 11. The first crimping part 12b is inserted
from outside the cover plate 3 to inside the cover plate 3, i.e.,
from the side of the cover plate 3 to the side of the current
collector 8. In this embodiment, the annular projection 11d of the
outer gasket 11 is inserted through the through-hole 3a of the
cover plate 3 and the through-hole 10b of the plastic plate 10.
This means when the first crimping part 12b is inserted through the
through-hole 11c of the outer gasket 11, the first crimping part
12b is also inserted through the through-hole 3a of the cover plate
3 and the through-hole 10b of the plastic plate 10.
[0097] The first crimping part 12b is sized so that its end
projects from the inner surface of the plastic plate 10 toward the
inside of the case 1 when it has been inserted through the
through-hole 3a of the cover plate 3, the through-hole 10b of the
plastic plate 10, the through-hole 11c of the outer gasket 11 and
the through-hole 8b of the current collector 8.
[0098] The first crimping part 12b has at its end an axially
extending non-through hole 12d. Thus, the end of the first crimping
part 12b has a hollow shaft shape. As shown in FIG. 6, the bottom
12e of the non-through hole 12d is located between the cover plate
3 and the current collector 8 with the end of the first crimping
part 12b crimped.
[0099] The non-through hole 12d is formed by a drill. In
association with this, the bottom 12e of the non-through hole 12d
has a tapered shape corresponding to the shape of the end of the
drill.
[0100] The end of the first crimping part 12b is squeezed outward
or flattened while being forced radially outward by crimping, so as
to be formed into a flange shape having a diameter larger than that
of a base end of the first crimping part 12b. That is, the end of
the first crimping part 12b has a diameter larger than that of the
through-hole 3a of the cover plate 3 after being crimped.
[0101] As a result, the body 12a and the flange shaped end of the
first crimping part 12b together hold the peripheries of the
through-holes 3a, 8b, 10b and 11c therebetween while bringing the
outer gasket 11 into close contact with the outer surface of the
cover plate 3 and bringing the plastic plate 10 into close contact
with the inner surface of the cover plate 3. This provides sealing
around the peripheries of the through-holes 3a, 8b, 10b and 11c,
thereby maintaining sealing within the case 1. As will be
understood, the crimping of the first crimping part 12b is carried
out prior to the welding of the cover plate 3 onto the case body
2.
[0102] As shown in FIGS. 7 and 8, the second crimping part 12c has
a solid shaft shape having a diameter smaller than that of the body
12a. The second crimping part 12c has a shaft diameter that allows
itself to be inserted into a later-described first through-hole 15a
formed in the drawing member 15. As shown in FIGS. 5 and 6, the end
of the second crimping part 12c is crimped with the second crimping
part 12c inserted through the first through-hole 15b of the drawing
member 15. Thus, the drawing member 15 is held between the body 12a
and the end of the second crimping part 12c deformed into a flange
shape, so as to be physically and electrically connected to the
rivet 12. The crimping of the second crimping part 12c is carried
out prior to the crimping of the first crimping part 12b.
[0103] The dimensional relationship among the through-hole 3a of
the cover plate 3, the through-hole 8b of the connection part 8a of
the current collector 8, the through-hole 10b of the plastic plate
10, the through-hole 11c and annular projection 11d of the outer
gasket 11, and the first crimping part 12b of the rivet 12 will be
described. As shown in detail in FIG. 5, the inner diameter of the
through-hole 3a of the cover plate 3 and the inner diameter of the
through-hole 10b of the plastic plate 10 are the same or
substantially the same. The inner diameter of the through-hole 3a
of the cover plate 3 and the inner diameter of the through-hole 10b
of the plastic plate 10 are the same or substantially the same as
the outer diameter of the annular projection 11d of the outer
gasket 11. The length of the annular projection 11d of the outer
gasket 11 is the same or substantially the same as the sum of the
thicknesses of the cover plate 3 and plastic plate 10. The inner
diameter of the annular projection 11d of the outer gasket 11 and
the inner diameter of the through-hole 8b of the connection part 8a
of the current collector 8 are the same or substantially the same.
The inner diameter of the annular projection 11d of the outer
gasket 11 and the inner diameter of the through-hole 8b of the
connection part 8a of the current collector 8 are the same or
substantially the same as the outer diameter of the first crimping
part 12b of the rivet 12. The length of the first crimping part 12b
of the rivet 12 is the same or substantially the same as the sum of
the thicknesses of the cover plate 3, the connection part 8a of the
current collector 8, the plastic plate 10, and the outer gasket
11.
[0104] Accordingly, the body 12a of the rivet 12 is inserted into
the recess 11b of the outer gasket 11, the first crimping part 12b
of the rivet 12 extends through the through-hole 11c at a bottom
surface of the recess 11b and is inserted into the through-hole 8b
of the connection part 8a of the current collector 8, and an end
portion of the first crimping part 12b projecting downward from the
through-hole 8b of the connection part 8a is crimped from below.
With this configuration, the rivet 12 is attached to the cover
plate 3 while the rivet 12 is electrically connected to the
connection part 8a of the current collector 8 and is insulated from
the cover plate 3.
[0105] The terminal retainer 13 is a synthetic resin with
insulating properties, like the plastic plate 10 and outer gasket
11. Note that a reinforced resin material obtained by uniformly
mixing polyphenylene sulfide resin with glass fiber as a filler,
for example, is used as the material for the terminal retainer 13
in order to make the hardness higher than those of the plastic
plate 10 and outer gasket 11. Alternatively,
polytetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA)
resin is used instead of polyphenylene sulfide resin. An inorganic
fiber other than glass fiber may be used. However, the material is
not limited to this, and any appropriate material can be selected.
However, the terminal retainer 13 may not have insulating
properties. When aluminum or an aluminum alloy is used as a
material for the case 1, the terminal retainer 13 of the positive
electrode may be non-isolated so that the potential of the positive
electrode may be identical with the potential of the case 1. This
suppresses corrosion of the case 1. When iron or stainless steel is
used as a material for the case 1, the terminal retainer 13 of the
negative electrode may be non-isolated so that the potential of the
negative electrode may be identical with the potential of the case
1. In order for the positive electrode or negative electrode and
the case 1 to have an identical potential, the terminal retainer 13
may comprise a material containing a conductive material carbon) as
well as a filler mixed therein so that the terminal retainer 13
becomes semi-conductive, for example.
[0106] The terminal retainer 13 is slightly larger than a head 14a
of the terminal bolt 14 and has a rectangular shape. The terminal
retainer 13 includes a surrounding circumferential outer wall part
13a at the outer periphery, which is formed by recessing an upper
surface except for the outer periphery. The terminal retainer 13
includes a recess 13b which can receive the head 14a of the
terminal bolt 14 inside the outer wall part 13a. The terminal
retainer 13 includes a non-circular fitting projection 13c in the
recess 13b. The fitting projection 13c fits in a non-circular
fitting recess (fitting groove) 14c formed in the head 14a of the
terminal bolt 14 while the recess 13b receives the head 14a of the
terminal bolt 14. Accordingly, when the fitting projection 13c in
the recess 13b (i.e., the fitting projection 13c at a lower
position than an upper end surface of the outer wall part 11a in
the recess 13b) fits in the fitting recess 14c of the head 14a of
the terminal bolt 14, the terminal retainer 13 receives the
terminal bolt 14 while the terminal bolt 14 is restrained from
rotating about its axis. Note that, in the present embodiment, the
fitting recess 14c of the terminal bolt 14 is formed by cutting out
a part extending from one side to the opposite side and has a
rectangular shape. The fitting projection 13c of the terminal
retainer 13 is formed to be rectangular so as to correspond to the
rectangular fitting recess 14c.
[0107] A lower surface of the terminal retainer 13 includes a
non-circular projection 13d. In the present embodiment, the
projection 13d is a rectangular projecting surface (raised
surface). A region of the upper surface of the cover plate 3 where
the terminal retainer 13 is arranged includes a non-circular recess
(second recess) 3c which can receive the projection 13d of the
terminal retainer 13. When the projection 13d of the terminal
retainer 13 is inserted into the second recess 3c, the terminal
retainer 13 is restrained from rotating about its axis, like the
outer gasket 11. Note that, in the present embodiment, the second
recess 3c is formed to be rectangular so as to correspond to the
rectangular projection 13d. The second recess 3c is formed by
coining or the like.
[0108] When the terminal retainer 13 is to be arranged on the upper
surface of the cover plate 3, the lower surface (including a
surface of the projection 13d) of the terminal retainer 13 is
treated by appropriate means so that the glass fiber is exposed at
the lower surface of the terminal retainer 13. A preferred example
of the appropriate means is to mechanically cut off the lower
surface of the terminal retainer 13. For example, the glass fiber
is exposed by cutting the lower surface of the terminal retainer 13
with a file or the like. The projection 13d at the lower surface of
the terminal retainer 13 fits in the second recess 3c at the upper
surface of the cover plate 3, and the terminal retainer 13 is fixed
to the upper surface of the cover plate 3. A method for fixing the
terminal retainer 13 to the cover plate 3 is not particularly
limited. For example, appropriate adhesive means (e.g., an adhesive
film, a liquid adhesive, or a solid adhesive) may be supplied to at
least one of the upper surface (in particular, the second recess
3c) of the cover plate 3 and the lower surface of the terminal
retainer 13, and the terminal retainer 13 may be fixed to the cover
plate 3 via the adhesive means. Although a common adhesive can be
used as the adhesive, an epoxy resin adhesive may preferably be
used. An epoxy resin has poor adhesion to the synthetic resin used
for the terminal retainer 13 but has good adhesion to an inorganic
fiber. Accordingly, the glass fiber exposed at the lower surface of
the terminal retainer 13 allows the terminal retainer 13 to be
firmly bonded to the cover plate 3.
[0109] The terminal bolt 14 is intended to electrically connect the
battery cell to an external device. The terminal bolt 14 is a
conductive metal member with high strength including iron, steel
such as stainless steel and chromium molybdenum steel, or the like.
As described above, the terminal bolt 14 includes the head 14a
sized to be inserted into the recess 13b of the terminal retainer
13 and a shaft 14b projecting from an upper surface of the head 14a
and having a male thread at an outer peripheral surface. A lower
surface of the head 14a includes a non-circular fitting recess
(fitting groove) 14c, as described above. Accordingly, when the
fitting projection 13c in the recess 13b fits in the fitting recess
14c, the terminal bolt 14 is insulated from the cover plate 3 and
is supported on the terminal retainer 13 while the shaft 14b is
restrained from rotating about its axis.
[0110] The drawing member 15 is a rectangular conductive metal
member including a copper alloy or the like. A surface of the
drawing member 15 is plated with nickel for preventing rust,
improving slipperiness, and other purposes. The drawing member 15
includes a first through-hole 15a at one end and a second
through-hole 15b at the other end. The second crimping part 12c of
the rivet 12 is inserted into the first through-hole 15a. The shaft
14b of the terminal bolt 14 is inserted into the second
through-hole 15b. An end portion of the second crimping part 12c of
the rivet 12 which projects upward from the first through-hole 15a
of the drawing member 15 is crimped from above. With the crimping,
the rivet 12 and drawing member 15 are integrated.
[0111] Note that, in the terminal bolt 14, the shaft 14b is simply
inserted into the second through-hole 15b of the drawing member 15.
However, for example, when a crimp contact of a lead wire of an
external device (not shown) fits on the shaft 14b of the terminal
bolt 14, and the shaft 14b of the terminal bolt 14 is fixed with a
nut, the terminal bolt 14 is slightly lifted, and the upper surface
of the head 14a comes into pressure contact with a lower surface of
the drawing member 15. This causes the crimp contact of the lead
wire together with the drawing member 15 to be held between the
head 14a of the terminal bolt 14 and the nut. With this
configuration, the crimp contact, terminal bolt 14, and drawing
member 15 are electrically connected to one another with
reliability. Accordingly, the crimp contact of the lead wire is
electrically connected to the electrode assembly 4 via the terminal
bolt 14, drawing member 15, rivet 12 and current collector 8 which
are insulated from the cover plate 3 by the terminal retainer 13,
outer gasket 11, and plastic plate 10. This causes the external
device to be electrically connected to the battery cell.
[0112] Additionally, the fitting recess 14c of the head 14a of the
terminal bolt 14 fitting on the fitting projection 13c in the
recess 13b of the terminal retainer 13 fixed on the upper surface
of the cover plate 3 reliably stops the terminal bolt 14 from
rotating together with the nut when the nut is fixed to the shaft
14b of the terminal bolt 14. Even if there is some clearance
between the fitting recess 14c of the head 14a of the terminal bolt
14 and the fitting projection 13c in the recess 13b of the terminal
retainer 13, the terminal bolt 14 only rotates idly by a certain
degree and poses no special problem.
[0113] At this time, since the terminal retainer 13 stops the
terminal bolt 14 from rotating, the terminal retainer 13 receives
rotational torque from the terminal bolt 14. However, the lower
surface of the terminal retainer 13 with the glass fiber exposed is
in intimate contact with the upper surface of the cover plate 3,
and therefore the terminal retainer 13 is fixed with increased
frictional resistance against the cover plate 3. Accordingly, the
terminal retainer 13 is reliably stopped from rotating together
with the terminal bolt 14 due to rotational torque from the
terminal bolt 14. The second recess 3c of the upper surface of the
cover plate 3 and the projection 13d at the lower surface of the
terminal retainer 13 fitting in with each other make the
rotation-stopping effect more remarkable. As described above, since
adhesive means (e.g., an adhesive) is supplied to one of the upper
surface (in particular, the second recess 3c) of the cover plate 3
and the lower surface of the terminal retainer 13, and the terminal
retainer 13 is fixed to the cover plate 3 by the adhesive means,
stopping of rotation is further ensured.
[0114] Note that if the perimeter of the shaft 14b (male thread
part) of the terminal bolt 14 is smaller, i.e., the shaft 14b of
the terminal bolt 14 has a smaller diameter, and a synthetic resin
such as polyphenylene sulfide resin (PPS) is used alone as the
material for the terminal retainer 13, the terminal retainer 13 may
not withstand rotational torque from the terminal bolt 14. However,
mixing of a synthetic resin with an inorganic fiber such as glass
fiber enhances the strength of the terminal retainer 13. The mixing
also contributes to cost reduction.
[0115] Since the terminal retainer 13 is provided separate from the
outer gasket 11 at the cover plate 3, rotational torque is not
transmitted to the outer gasket 11, which seals up a gap around the
rivet 12. Accordingly, unintentional force is not applied to the
outer gasket 11. Sealing with the outer gasket 11 (more
specifically, sealing between the lower surface of the outer gasket
11 and the upper surface of the cover plate 3 (an upper surface of
the first recess 3b), sealing between an outer peripheral surface
of the annular projection 11d of the outer gasket 11 and an inner
peripheral surface of the through-hole 3a of the cover plate 3 and
an inner peripheral surface of the through-hole 10b of the plastic
plate 10, and sealing between an inner peripheral surface of the
annular projection 11d of the outer gasket 11 and an outer
peripheral surface of the first crimping part 12b of the rivet 12)
is not impaired.
[0116] Rotational torque applied to the shaft 14b of the terminal
bolt 14 is not transmitted to the rivet 12, which is provided
separate from the terminal bolt 14. Accordingly, a situation does
not occur in which rotation of the rivet 12 causes the rivet 12 and
the connection part 8a of the current collector 8 fixed by crimping
to come loose to impair the connection therebetween. Additionally,
unintentional force is not applied to the plastic plate 10 and
outer gasket 11. Further, sealing with the plastic plate 10 and
outer gasket 11 (more specifically, sealing between an upper
surface of the plastic plate 10 and the lower surface of the cover
plate 3, sealing between the lower surface of the outer gasket 11
and the upper surface of the cover plate 3 (the upper surface of
the first recess 3b), sealing between the outer peripheral surface
of the annular projection 11d of the outer gasket 11 and the inner
peripheral surface of the through-hole 3a of the cover plate 3 and
the inner peripheral surface of the through-hole 10b of the plastic
plate 10, and sealing between the inner peripheral surface of the
annular projection 11d of the outer gasket 11 and the outer
peripheral surface of the first crimping part 12b of the rivet 12)
is not impaired.
[0117] The separate provision of the outer gasket 11 and the
terminal retainer 13 allows appropriate selection of a material
with suitable hardness for a sealing member as the material for the
outer gasket 11 and appropriate selection of a material with
sufficient hardness to withstand rotational torque from the
terminal bolt 14 as the material for the terminal retainer 13. More
specifically, since the outer gasket 11 has a greater sealing
effect when the outer gasket 11 deforms elastically to come into
intimate contact with surfaces of the conductive members (the cover
plate 3, current collector 8, and rivet 12), the outer gasket 11 is
required to have a certain degree of flexibility. If the terminal
retainer 13 is highly flexible, rotational torque from the terminal
bolt 14 makes the fitting projection 13c likely to be worn and
chipped. As the wear progresses, the rotation-stopping function of
the terminal bolt 14 is impaired. For this reason, the terminal
retainer 13 is required to have rigidity enough to withstand
rotational torque from the terminal bolt 14.
[0118] In the rivet 12 according to the present embodiment, the
dimension in an axial direction of the body 12a is set to be larger
than that of a conventional one so as to prevent or reduce plastic
deformation across the rivet 12 caused by crimping by the first
crimping part 12b and second crimping part 12c. As a result, the
position in height of the drawing member 15 from the upper surface
of the cover plate 3 is necessarily higher than that in a
conventional terminal structure. The fitting projection 13c of the
terminal retainer 13 according to the present embodiment is a part
which directly receives rotational torque from the terminal bolt 14
when the terminal retainer 13 stops the terminal bolt 14 from
rotating. Accordingly, the fitting projection 13c of the terminal
retainer 13 needs to have a sufficient thickness in a direction of
height so as to have strength enough to withstand rotational
torque. As a result, the position in height of the head 14a of the
terminal bolt 14 is high, and the position in height of the drawing
member 15 from the upper surface of the cover plate 3 is also
necessarily higher than that in a conventional terminal structure.
For this reason, in the present embodiment, the outer wall part 11a
of the outer gasket 11 is high, and the creepage distance from the
upper surface of the cover plate 3 to the upper end surface of the
outer wall part 11a is long (the ratio of the creepage distance to
the width dimension of the cover plate 3 is preferably 0.15 to
0.3). The outer wall part 13a of the terminal retainer 13 is high,
and the creepage distance from the upper surface of the cover plate
3 to an upper end surface of the outer wall part 13a is long (the
ratio of the creepage distance to the width dimension of the cover
plate 3 is preferably 0.15 to 0.3).
[0119] More specifically, the outer wall part 11a of the outer
gasket 11 is formed so as to entirely or substantially entirely
cover the body 12a of the rivet 12 and such that the upper end
surface of the outer wall part 11a is in contact with or is
slightly spaced from the lower surface of the drawing member 15.
The outer wall part 13a of the terminal retainer 13 is formed so as
to entirely or substantially entirely cover the head 14a of the
terminal bolt 14 and such that the upper end surface of the outer
wall part 13a is in contact with or is slightly spaced from the
lower surface of the drawing member 15.
[0120] With the above-described configuration, even if the battery
cell is exposed to droplets of water generated by condensation or
the like or a conductive atmosphere (static electricity or dust),
the outer wall part 11a of the outer gasket 11 and the outer wall
part 13a of the terminal retainer 13 serve as covers (or barriers).
This conveniently prevents a short between the cover plate 3 and
the rivet 12 and a short between the cover plate 3 and the terminal
bolt 14.
[0121] According to the thus described battery cell of this
embodiment, the first crimping part 12b of the rivet 12 is crimped
at its end in a state where it is inserted through the outer gasket
11, the cover plate 3, the plastic plate 10 and the current
collector 8. When the end of the first crimping part 12b is
crimped, the first crimping part 12b applies force to press the
cover plate 3 in the direction orthogonal to the axis of the rivet
12. When this takes place, the bottom 12e of the non-through hole
12d in the end of the first crimping part 12b is located between
the cover plate 3 and the current collector 8. With this
arrangement, the first crimping part 12b is prevented from being
pressed to expand toward the hollow portion in the vicinity of the
cover plate 3. That is, this arrangement provides close contact
between the first crimping part 12b and the cover plate 3, and thus
reliably generates force causing the first crimping part 12b to
press the cover plate 3. This ensures sealing between the cover
plate 3 and the first crimping part 12b. What is more, the end of
the first crimping part 12b has a hollow shaft shape, which ensures
that deformation of the end of the first crimping part 12b into a
flange shape is reliably achieved while eliminating the need for
repeated crimping operations. Furthermore, the deformation of the
first crimping part 12b into a flange shape allows the first
crimping part 12b to press the cover plate 3 and the current
collector 8 in the direction parallel to the axis of the rivet 12.
With this, the plastic plate 10 arranged between the cover plate 3
and the current collector 8 and the outer gasket 11 arranged
between the cover plate 3 and the body 12a are tightly pressed in a
reliable manner, thereby ensuring sealing of the case 1.
[0122] With reference to FIG. 6, the first crimping part 12b of the
rivet 12 has a solid portion around the through-hole 3a of the
cover plate 3. Because of this, force is generated in the direction
indicated by arrow A at the time of crimping, thereby ensuring
sealing between the cover plate 3 and the rivet 12. The first
crimping part 12b is hollow at the end, and therefore the end of
the first crimping part 12b is deformed into a flange shape in a
reliable manner at the time of crimping. As a result, force is
generated in the direction indicated by arrow B so that the outer
gasket 11, the cover plate 3, the plastic plate 10 and the current
collector 8 are tightly pressed against each other, thereby
ensuring sealing of the case 1.
[0123] The outer gasket 11 is arranged between the body 12a and the
cover plate 3 at a location close to the body 12a of the rivet 12,
and the plastic plate 10 is arranged between the cover plate 3 and
the current collector 8 at a location close to the first crimping
part 12b of the rivet 12. The end of the first crimping part 12b is
crimped in this state. Because of this, the force, which is
generated in the direction parallel to the axis of the rivet 12
when the end of the first crimping part 12b is deformed into a
flange shape, is transmitted to the areas between the cover plate 3
and the current collector 8 and between the cover plate 3 and the
body 12a. As a result, the plastic plate 10 and the outer gasket 11
are tightly pressed in a reliable manner, thereby maintaining
sealing of the case 1 more effectively.
[0124] Furthermore, the annular projection 11d of the outer gasket
11 is inserted through the cover plate 3 while covering the outer
circumference of the first crimping portion 12b, and therefore the
outer gasket 11 is arranged to extend through between the cover
plate 3 and the body 12a and between the cover plate 3 and the
first crimping part 12b. With this arrangement, the outer gasket 11
arranged between the cover plate 3 and the body 12a and between the
cover plate 3 and the first crimping part 12b is tightly pressed by
the force generated by the crimping of the first crimping part 12b,
thereby making it possible to maintain sealing of the case 1 more
effectively.
[0125] Furthermore, the end of the first crimping part 12b is
crimped to have a thickness, which decreases as it advances away
from the axis of the first crimping part 12b. This increases the
degree of contact between the end of the first crimping part 12b
and the cover plate 3 or the current collector 8.
[0126] Note that an electric storage device according to the
present invention is not limited to the above-described embodiment
and that various changes may be made without departing from the
spirit and scope of the present invention.
[0127] For example, in the above embodiment, the bottom 12e of the
non-through hole 12d is located more internally in the case 1 than
the inner surface SF of the cover plate 3. However, the present
invention is not limited to this. For example, the bottom 12e of
the non-through hole 12d may be located at the same or
substantially the same level as the inner surface of the cover
plate 3. In this arrangement too, only the end of the first
crimping part 12b has a hollow shaft shape, and therefore the end
of the first crimping part 12b can be formed into a flange shape
necessary and sufficient to hold the plastic plate 10 and the outer
gasket 11 therewith in a reliable manner.
[0128] The above embodiment has illustrated an example in which: on
the premise that the first crimping part 12b is inserted through
the cover plate 3 from outside the case 1 to inside the case 1, the
end of the first crimping part 12b, which is to be located inside
the case 1, is crimped. However, the present invention is not
limited to this. For example, the rivet 12 may be made up of the
body 12a and the first crimping part 12b and the first crimping
part 12b may be inserted through the cover plate 3 from inside the
case 1 to outside the case 1, so that the end of the first crimping
part 12b, which is to be located outside the case 1, may be
crimped.
[0129] FIG. 9 illustrates a specific example of this. The terminal
structure 9' includes a rivet 12' that is inserted through the
cover plate 3' from inside the case 1' to outside the case 1'. The
rivet 12' includes a body 12a' that is electrically connected to
the electrode assembly (not shown) and an insertion part 12b' that
is formed continuously with the body 12a' and inserted through the
cover plate 3'. A plastic plate 10 is arranged on the inner surface
of the cover plate 3', and an outer gasket 11' is arranged on the
outer surface of the cover plate 3'. A drawing member 15' as a
conductive member is arranged on the outer surface of the outer
gasket 11'. The insertion part 12b' of the rivet 12' is inserted
through the plastic plate 10', the cover plate 3', the outer gasket
11' and the drawing member 15' in this order. Then, the end of the
insertion part 12b' projecting from the drawing member 15'
crimped.
[0130] The above embodiment has illustrated an example in which the
body 12a of the rivet 12 has a shaft shape. However, the present
invention is not limited to this. The body 12a of the rivet 12 may
have any shape as long as it is not inserted through the cover
plate 3, the current collector 8 and the like through which the
first crimping part 12b is inserted, without being limited to a
particular shape. In this respect, the body 12a of the rivet 12 may
have a thin plate shape, for example.
[0131] The above embodiment has also illustrated an example in
which the entire lower surface of the outer gasket 11 fits in the
first recess 3b in the upper surface of the cover plate 3.
Alternatively, a projection may be formed at the lower surface of
the outer gasket 11, the first recess of the cover plate 3 may be
sized to receive the projection, and the projection of the outer
gasket 11 may fit in the first recess, as with the case of the
terminal retainer 13.
[0132] The above embodiment has also illustrated an example in
which the projection 13d is formed in the lower surface of the
terminal retainer 13, the second recess 3c sized to receive the
projection 13d is formed in the upper surface of the cover plate 3,
and the projection 13d of the terminal retainer 13 fits in the
second recess 3c of the cover plate 3. Alternatively, the
projection 13d may not be formed, the second recess of the cover
plate 3 may be sized to receive the entire lower surface of the
terminal retainer 13, and the entire lower surface of the terminal
retainer 13 may fit in the second recess, as with the case of the
outer gasket 11.
[0133] It is preferred, however, that the cover plate 3 have the
first recess 3b and second recess 3c because they can increase the
moment of area of the cover plate 3, which results in enhancement
of the mechanical strength of the cover plate 3. In this instance,
reducing the size of one of the first recess 3b and the second
recess 3c increases the distance between the first recess 3b and
the second recess 3c. This prevents the first recess 3b and second
recess 3c from affecting each other. The above embodiment has
illustrated an example in which the first recess 3b for the outer
gasket 11 is larger than the second recess 3c for the terminal
retainer 13. This configuration is adopted on the ground that the
flatness and mechanical strength of the cover plate 3 increase with
an increase in the area of the first recess 3b, which results in an
increase in sealing effect and durability.
[0134] For either the outer gasket 11 or the terminal retainer 13,
the number of projections is not limited to one, and a plurality of
projections may be formed. The outer gasket 11 and terminal
retainer 13 need not be rectangular. For example, the outer gasket
11 and terminal retainer 13 may be circular, hexagonal, or
octagonal.
[0135] The above embodiment has illustrated an example in which the
current collector 8 for the positive electrode and the rivet 12 for
the positive electrode include aluminum or an aluminum alloy while
the current collector 8 for the negative electrode and the rivet 12
for the negative electrode include copper or a copper alloy.
However, any materials may be used as long as the materials are
conductive metal materials appropriate to the type of a battery
cell. The above embodiment has also illustrated the materials for
the terminal bolt 14 and drawing member 15. However, any materials
may be used as long as the materials are conductive metal materials
whose properties such as strength and conductivity are
appropriate.
[0136] The above embodiment has illustrated an example in which the
shaft (male thread part) 14h projects from the upper surface of the
head 14a of the terminal bolt 14. However, a shaft in an
appropriate form such as a circular or polygonal tube may project
instead of the male thread part, and a threaded hole may be formed
in an upper end surface of the shaft.
[0137] The electrode assembly is not limited to one of the winding
type in the form of an elliptic cylinder as described in the above
embodiment. The electrode assembly may have any other shape and may
be one of the stacked type.
[0138] The above embodiment has illustrated an example in which the
terminal structure 9 is arranged on the cover plate 3, but
alternatively the terminal structure 9 may be arranged on the case
body 2. That is, the rivet 12 may extend through the case body 2.
In this instance too, an O-temper material may preferably be used
for the case body 2. As will be understood, the case body 2 may
include other aluminum alloys than an O-temper aluminum alloy or
other metallic materials.
[0139] In the above embodiment, the rivet 12 is crimped at both
ends (the ends of the first crimping part 12b and the second
crimping part 12c). However, the present invention is not limited
to this. For example, the rivet 12 may be made up of the body 12a
and the first crimping part 12b, and the end of the first crimping
part 12b may be crimped.
[0140] In the above embodiment, the rivet 12 and the terminal bolt
14 are separate components, which are electrically connected to
each other via the drawing member 15. However, the present
invention is not limited to this. For example, the rivet 12 and the
shaft 14b of the terminal bolt 14 may be integrally formed. In this
instance, the terminal retainer 13 is unnecessary.
[0141] In the above embodiment, the outer gasket 11 and the
terminal retainer 13 are separately arranged on the outer surface
of the cover plate 3, but the present invention is not limited to
this. For example, the outer gasket 11 and the terminal retainer 13
may be integrally formed.
[0142] In the above embodiment, the outer gasket 11 has an annular
projection 11d that is fitted into the through-hole 3a of the cover
plate 3, but the present invention is not limited to this. For
example, the plastic plate 10 may have an annular projection that
can be fitted into the through-hole 3a of the cover plate 3.
Alternatively, the outer gasket 11 and the plastic plate 10 may
each have an annular projection that can be fitted into the
through-hole 3a of the cover plate 3.
[0143] The above embodiment has been described in the context of a
lithium ion secondary battery cell. However, the type and size
(capacity) of a battery cell may be arbitrarily selected.
[0144] The present invention is not limited to lithium ion
secondary battery cells and can also be applied to various
secondary battery cells, primary battery cells, and capacitors such
as an electric double layer capacitor.
[0145] In the above embodiment, the end of the first crimping part
12b of the rivet 12 is crimped to directly apply compression force
to the periphery of the through-hole 8b of the connection part 8a
of the current collector 8. However, the present invention not
limited to this. For example, a washer may be arranged on the
connection part 8a, and the first crimping part 12b may be inserted
through the through-hole 8b of the connection part 8a and a
through-hole of the washer, so that the end of the first crimping
part 12b projecting from the washer may be crimped. This allows the
compression force by the crimped end of the first crimping part 12b
to be applied to the washer, thereby making it possible to enhance
the mechanical strength of the connection part 8a of the current
collector 8.
* * * * *